The switch component of an electrical wiring device typically includes a user accessible switch arm, rocker paddle, push button, touch pad, etc. (“switching surface”), a lever arm or suitable linkage attached to the backside of the switching surface, and a line side contact that can be connected/disconnected from a load side contact via operation of the switching surface by the user. A common single switch device for activating a remote receptacle or light, for example, typically presents the switching surface in the center of the electrical wiring device having an on/off motion along the longitudinal axis of the device. When two switches are presented on a single electrical wiring device, or a switch and a receptacle, for example, are presented on a single device, the switching surface(s) operates in a direction that is transverse to the length of the device. Accordingly, switch placement, orientation, size and ergonomics become considerations in modern, functional and aesthetic switch design.
Safety is a further major consideration in the design and operation of electrical wiring devices. For example, a receptacle disposed in an electrical distribution system may supply power through a user attachable plug to a load or to other receptacles. In certain environments where a greater likelihood for an electrical shock hazard exists, such as in a residential bathroom or kitchen, for example, the receptacle may include a circuit protection component, e.g., a ground fault circuit interrupter (GFCI). However, the use of wiring devices having a circuit protection component or capability is in no way limited to this exemplary environment. GFCIs have been known for many years. Their intended purpose is to protect the electrical power user from electrocution when a hazardous ground fault condition is present. Ground fault conditions are an unintended current path from the line conductor having faulty or damaged insulation to ground. The shock hazard occurs when someone contacts ground and the line conductor at the same time. A fire hazard may occur if the ground fault current results in sufficient heating to ignite nearby combustibles. GFCIs configured to prevent fire but not necessarily protect a user from electrocution are known as ground fault equipment protectors (GFEPs.)
Other known protective devices include arc fault circuit interrupters (AFCIs). Their intended purpose is to protect the electrical power user from fire when a hazardous arcing condition is present. Hazardous arc fault conditions (known as series arc faults) may result from a poor electrical connection in the electrical distribution system supplying power to the load. Hazardous arcing conditions (known as parallel arc faults) may occur between a line to line conductor, line to neutral conductor, or line to ground conductor, due to faulty or damaged insulation. The heat associated with the arc fault condition may be sufficient to ignite nearby combustibles.
Known protective devices such as GFCIs, GFEPs, AFCIs or combinations of such devices are configured to protect an electrical distribution system from at least one fault condition. Such devices are typically provided with line terminals for coupling to the supply voltage of the electrical distribution system, and load terminals coupled to the protected portion of the system and a circuit interrupter for disconnection of the load terminals from the line terminals. Load terminals may include plug receptacles for electrical connection of a user attachable load through a plug. Load terminals may include feed-through terminals for attachment to other receptacles. The protective device may be provided with a sensor for sensing the fault, a detector for establishing if the sensed signal represents a true hazardous fault, as opposed to electrical noise, and a switch responsive to the detector sensor, wherein the circuit interrupter comprising the contacts of a relay or trip mechanism are operated by a solenoid responsive to the switch to disconnect the load terminals from the line terminals. The disconnection is also known as tripping. A power supply may be required to furnish power to the sensor, detector, switch or solenoid.
One disadvantage of known combination devices, herein illustrated as a switch in combination with a protection component, is that the user accessible switch toggles in a motion that is parallel to the minor (latitudinal) axis of the device. The user of the device does not find such rocking motion to be ergonomic. Another disadvantage is that such rocking motion is not consistent with other wiring devices whose rocking motion is perpendicular to the minor axis of the device. Another disadvantage of known combination devices is that the user accessible switch portion of the combination device has been limited in number to a single switch.
Another disadvantage of known switch assemblies and combination devices is that the user accessible switch portion may fail to open because the switch contacts permanently remain in the closed position. Such permanent switch closure may occur for the following reasons: The contacts of the switch erode during opening and closing actuations until the contacts metallurgically bond (weld) together. Such erosion is caused by electrical arcing that occurs when the switch is called upon to make or break load current. Arcing during contact mating (contact closure) occurs in the following manner. At the moment of closure one contact strikes the other. Load current is established, but the striking motion causes the contacts to momentarily repel apart (known as contact bounce.) Even though the contacts have separated, load current continues by way of an electrical arc. The temperature of the arc is greater than the melting point of the contact material, causing contact material to melt. The contacts reclose after the bounce energy has dissipated, at which time the electrical arc extinguishes. However, when the contacts reclose, there is a layer of molten contact material between the two contacts that solidifies once the contacts are closed and there is no longer heat generated by the arc. If the bounce is severe enough, the resulting molten material is sufficient to permanently join the contacts together, that is, the switch mechanism is incapable of breaking the weld connection. During contact break (contact opening), load current does not immediately stop flowing the moment that the contacts open. For DC electrical distribution systems, an electrical arc is generated when the contacts open that continues until the contacts have become sufficiently separated from each other. For AC electrical distribution systems, the arc continues until a zero-crossing in the load current occurs or until the contacts become sufficiently separated, whichever happens first. The arc energy during contact opening roughens the surfaces of the contacts that mate with each other during the next closing operation, which exacerbates welding due to contact bounce. In general, the amount of heat generated by an arc increases as the distance between the contacts during the arcing event increases. Another cause of contact erosion includes mechanical abrasion of the contacts during repeated opening and closing operations. Permanent switch closure can also result from contaminants in the vicinity of the switch. Such contaminants can cause the switch contacts to corrode together. Also, contaminants of a particulate nature can impede the motion of the moving parts in the switch assembly, thus preventing the opening of the switch contacts.
In view of the foregoing and other reasons that will be recognized by those skilled in the art, the inventors have recognized a need to provide a compact switch assembly for use in an electrical wiring device that is functional and ergonomic. There is also a recognized need for a combination device (i.e., circuit interrupter and one or more switch assemblies) that is ergonomic and convenient to use. There is a further recognized need for a switch that can be opened and closed reliably under expected use conditions.